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Object/Subject Review: Sunwayman T20CS

Sunwayman is quickly becoming one of the top flashlight makers around. They are well known for a sleek look to their lights, and not compromising on quality. Their V series lights are the essence of simplicity in a UI. Recently Sunwayman released the T40CS, a foray into the realm of "tactical" lights. Now, they've made available the T20CS, the little brother to the T40CS. The T20CS is a compact thrower, using the top-of-the-line Cree XM-L U2 emitter in a large head with a deep reflector. Also, the T20CS features a side switch and a low voltage indicator light, which sets this light above the norm in this category.

Thanks to Sunwayman for providing the T20CS for review.

I’ll be reviewing the T20CS in two sections: first, I’ll discuss the light objectively (the facts about the light itself), then I’ll discuss the light subjectively (my impressions about the light's performance when used for specific applications). Sunwayman classifies this as a "tactical" light, so the subjective portion will look at it from that point of view. If you have any other specific applications you'd like the light tested for, let me know and I'll see what I can do.

The T20CS comes in a cardboard box that looks like it could be standard for many different Sunwayman lights, with a sticker on the side with the model number and a few specs.

Upon opening the box, you find the light nestled in some soft foam material attached to the box, and a sticker telling you that there is more stuff underneath the packing material. Included is the T20CS user manual, warranty card, ad card for other SWM lights, holster, lanyard, spare switch boot, and spare o-rings.

Construction Quality

This light feels extremely solid and well made, and has the attention to aesthetics that we've come to expect from Sunwayman.

Here's the T20CS compared in size to a 18650 battery:

As you can see, the battery accounts for a little more than half the length of the light, with a lot of length devoted to a deep reflector on the head for long throw.

The head has a mildly aggressive look to it, with a smooth stainless steel bezel. The side switch is a small black rubber button on the same part of the light that houses the emitter. To either side of the button you can see the fins that Sunwayman has put in for heat dissipation. They're a little smaller than you world normally see for cooling fins, but the head of the light itself is large enough to add a lot of surface area for cooling. The anodizing is dark grey color with just a hint of olive green when you look at it in the light, but otherwise just seems black at first glance. The lettering on the body is white and clearly printed, with the SWM logo on one side and the model number on the other. A rubber grip ring is included on the body. The tail cap has a bit of knurling to help with battery changes; this is the only knurling on the light. The switch extends well beyond the tail of the light, making it very easy to find and press, but making it impossible for the T20CS to tail stand.

Here's a shot of the side switch from the side, you can see it has a very low profile, so you shouldn't have to worry about it getting caught or worn away on anything.

On the side of the head, opposite the side switch, is the low voltage indicator, a red LED, inside a clear window into the head of the light. The indicator is flush with the head. I've included a description of the low voltage indicator in the "Performance" section of the review.

The grip ring on the body is made of a firm rubber. It can be moved to either end of the body with mild resistance, but I couldn't remove it from the body without applying more force than I felt comfortable subjecting it to. The detailing on the head of the light also provides a good amount of grip on the light.

The T20CS unscrews by hand into four pieces. (I was also able to unscrew the bezel by pressing it against a piece of rubber, making bezel replacements possible.)

You can see it has o-rings at each detachment to prevent water from getting in. All the threads are square cut to make them last longer and give a better feel to screwing and unscrewing each part. Most of the threads are anodized to improve durability, and on the tail cap it allows the light to be locked out (pressing the switch won't turn it on in your pocket or bag) by unscrewing it only about 3 degrees. Having such a small amount or turning need to put the light into lockout means the tail will still be very secure when in lockout mode, but it also means you have to be very sure the tail is fully tightened when you are ready to use the light, because there is small room for error. Having the threads between the body and head left bare will improve the electrical connection and allow the light to work even if not fully tightened in that area, but they will wear down faster. However, you shouldn't need to be unscrewing that part too often, because battery changes can be done at the tail (which has less friction anyway).

The rubber boot on the tail cap is imprinted with the Sunwayman logo, like most of their lights. There is a spring inside the tail for the negative batter contact. This is a forward clicky switch. Forward clicky switches allow momentary on by half-pressing the switch or constant on by with a full-press, clicking it into position, but tend to wear out a little easier than reverse clicky switches.

The head also has a spring for the positive battery contact, so the T20CS is set up to accept a wide range of battery lengths and also not loose connection during impacts. The emitter sits in the middle a white plastic housing. Because the reflector can be easily unscrewed from the rest of the head, you can use the T20CS in "candle mode" with the bare emitter, and it is recessed inside the head enough to still give it a slight amount of protection. However, it will no longer be waterproof, and will be vulnerable to scratching up the emitter. The T20CS uses the U2 binned XM-L emitter, which is on average about 7% brighter than the T6 bin, the most commonly used bin for high-quality lights in this class at this time (12/21/12).

You can see the underside of the emitter here, it fits nicely into the plastic housing and over the emitter. The use of plastic instead of metal is probably to keep heat from transferring directly into the reflector, and instead direct it to the outer body of the light, where your hand take take it away. The reflector on the T20CS is very smooth (SMO), as opposed to an "orange peel" (OP) texture. An OP reflector will make the beam look smoother by scattering out the light a bit, but an SMO will throw the light farther by not scattering it out. SMO reflectors typically show more rings, unevenness, or other artifacts in the beam, but on a light designed to throw long distances, this isn't too important. You can see the "Action Shots" section for pictures of the beam.

Here's some shots of the T20CS in the included holster. It's the typical SWM style holster, velcro for both the front flap and the belt strap, and the SWM logo printed in red on a tag.

The lanyard included is the typical SWM style lanyard. A lobster-claw attaches the lanyard to the light, a tab on the end of the lanyard, and an adjustable slider in the middle. A metal ring with a protrusion for the lanyard is included to be put on the light when you want to use the lanyard, because there is no lanyard hole anywhere on the T20CS.

There are two points where the lanyard ring can slide onto the T20CS, between the body and tail or between the body and head. However, between the body and tail the ring is very loose, because the body and tail don't pinch together on it. Between the body and head, the lanyard ring is very tight, but...

As you can see by this picture, I damaged the anodizing and o-ring trying to get it on. The diameter here must be slightly larger, because I had to push to get the ring on and it scratched things up a bit. There were no instructions or pictures included about where the ring is supposed to go, but I'm going to recommend putting it in between the body and tail unless you want to try to stretch it out with a tool to fit up by the head better.

User Interface

First, I'll clear something up from Sunwayman's specs on the T20CS. According to Sunwayman, the T20CS has Turbo, High, Medium, and Low modes, with hidden Strobe and SOS. On my reading of the specs, it sounded like Turbo was not available when using 1x18650. However, as you can see in the graphs below, it does do Turbo mode, just not regulated, and it's not much different from High mode.

The T20CS has two switches, the "forward clicky" tail switch and the "soft press" side switch.

To turn the light on, you first have to press the tail switch. If the tail cap switch is off, the side switch doesn't do anything. Whenever you press the tail cap switch, it will put the light in Turbo mode. Because it's a forward clicky, you can do a half-press for momentary Turbo, or a full press for constant Turbo. Once the light is on, you can either turn it off by the tail cap (and the side switch will continue to do nothing) or you can turn it off by a single press to the side switch which will leave the light in a sort of standby. When in standby, the light can be turned on by the side switch. The side switch always starts in High mode, and by holding down the side switch for about a second you can cycle High-Medium-Low. Turbo cannot be accessed by the side switch, you need to click the light off then back on by the tail switch. Also, when the light is on or in standby (the tailcap switch is fully pressed), you can do a quick double-click on the side switch to go into strobe mode. When in Strobe mode, you can do another quick double-click on the side switch to go into SOS. Turning the light off by either switch at any time will deactivate the Strobe or SOS and take you back to the regular UI.

There is a sort of mode memory. When you set the light to either High, Medium, or low, then turn it off by the side switch, it remembers the mode you were in and turns back on in that mode when you hit the side switch again. Turning the light off by the tail switch clears the mode memory. If you use the strobe or SOS modes, they will be ignored by the memory: they will not be remembered and will also not clear the memory. So, if you have it in High, Medium, or Low, then switch to Strobe or SOS, when you turn it off then back on by the side switch, it will go back to either High, Medium, or Low, whichever you used before activating the strobe.

A video showing the various aspects of the UI:

Action Shots

The T20CS in hand:

White Wall Beam Profiles:(photos taken at ISO 100, f/6.3, 1/4")

Low, Medium, High, Turbo

The T20CS outdoors: (photos taken at ISO 100, f/6.3, 15")

Barn; ~35 yards; Control, Low, Medium, High, Turbo

Barn; ~100 yards; Control, Low, Medium, High, Turbo

Barnyard, Yard; Turbo

Silo, ~1/3 mile (zoomed in), Control, Turbo
(you might have turn up your monitor's brightness for this one, it appears brighter than this in real life)

Bike Path, Control, Turbo
(ISO 100, f/3.3, 5")

Performance

I submerged the T20CS in about a foot of water, and clicked both the tail cap and side switches several times over the course of 10 minutes, with no evidence of water entering any part of the light, so it does appear to be waterproof.

Sunwayman claims this light to have a "constant current circuit", which means no pulse width modulation. I could find no trace of visible PWM on any mode, and no audible whine or buzz.

Sunwayman's specs for the T20CS mention using the light with 2xCR123 or 1x18650, but they also state that it can handle up to 10V. So, I've tested it with 2x16340 lithium-ion cells as well (total 8.4 V fully charged). As you'll see, this gives it super short runtimes and the low voltage indicator doesn't work, but the light does operate just fine, so this is an option if you want it.

Low Voltage Indicator

The T20CS features a red low voltage indicator LED on the body of the light, opposite the side switch. This LED kicks on when the battery reaches a certain voltage, then starts flashing at about 2-3 flashes per second when the battery hits a lower voltage. In my tests, I found the voltage that turns on the indicator to be different for each level. On the turbo and high modes it just goes straight from off to solid on to flashing. On the medium and low modes, there is a time when it sort of flashes intermittently as the battery approaches the voltage that activates the indicator, possibly because the voltage wavers as it sags. Then, as it is solid and approaches the voltage where it will strobe, it will flash intermittently for a while before going into a steady flash, presumably for the same reason. Below is a video of the indicator going to solid then flashing, and the results from my tests showing at what voltage the low voltage indicator lights up:

2x16340The low voltage indicator did not come on at all, in any mode, before the protection circuits in my 2x16340 cells cut them off. Instead, the XM-L emitter just started flashing, presumably to let me know the driver was no longer able to pull the necessary current out of the cells. I suppose that SWM designed it this way to avoid having the low voltage indicator come on when you pop in two fresh CR123 primaries. Below are the volages when the emitter started flashing using my 2x16340 cells, but this might be different for different brands of cells, if the driver is sensing a current drop instead of a voltage drop, as I suspect. Also, once the emitter started flashing, I was not able to switch to any different modes.
Turbo: 6.55V
High: 6.33V
Medium: 5.82V
Low: 6.23V

Current Draw

These measurements are made at the tail cap within a few seconds of turning on the light with fresh/fully charged batteries.

Note: The vertical axis of these charts represents a relative brightness measurement using a home made light box. The horizontal axis is time in hours:minutes:seconds. Runtimes are stated in hours:minutes.

This first set of charts compare the output of different batteries on each mode. On each mode I tested the T20CS with 2x16340 Ultrafire 880 mAh and 1x18650 Trustfire 2400 mAh. I normally don't use CR123's for runtime tests because of the expense, but I went ahead and did for the turbo mode here. When the 2x16340's finish, they rapidly drop output then go into a trobe mode, fast at first, then slowing down. The 1x18650 just gets dimmer as the battery runs down. On 2xCR123, the light gets dim, then starts a sort of "pulsing". It doesn't blink on and off, but rather pulses it's out put slightly, and the pulsing gradually gets dimmer.

Turbo (*Graph truncated to show detail*)

Turbo 2xCR123
Time Regulated: 0:38:04
Time to 50%: 0:39:39, 1:03:03 (drops past 50%, then back up, then down again)
Time until "pulsing": 4:26:44
Full Runtime: 27:30:00 (approximately)

Turbo 2x16340
Time Regulated: 0:19:17
Time to 50%: 0:19:47
Time Until Blinking: 0:27:16
Full Runtime: 1:11:51

Turbo 1x18650
Time Regulated: 0:01:09
Time to 50%: 1:31:33
Full Runtime: 4:52:53

High

High 2x16340
Time Regulated: 0:29:30
Time to 50%: 0:29:35
Time Until Blinking: 0:30:11
Full Runtime: 0:45:46

High 1x18650
Time Regulated: 1:02:35
Time to 50%: 1:56:30
Full Runtime: 6:36:03

Medium

Medium 2x16340
Time Regulated: 1:56:40
Time to 50%: 2:10:38
Time Until Blinking: 2:11:22
Full Runtime: 8:15:10

Medium 1x18650
Time Regulated: 10:50:59
Time to 50%: 11:04:19
Full Runtime: 14:30:22

These next two graphs are comparisons of the output of the different modes on each battery type.

2x16340
The T20CS blinks as the 2x16340's wear down.

1x18650
The T20CS gets dim as the 1x18650 wears down.

Subjective Review

General

Overall, the T20CS is another great offering from Sunwayman. It's got a great combo of function and style that is hard to beat.

Here are some of the highlights of what I like about the T20CS:
-compact with high output and long throw
-smooth reflector for throw
-"candle" mode
-low voltage indicator
-UI is reliable, no flickering or mode mistakes
-accepts many batteries
-attractive anodizing color and body design
-easy tail cap lockout (only a few degrees of rotation needed)
-side switch has a traditional flashlight feel
-great tint for a U2 bin!
-minimal rings/beam artifacts even at close distance

Here are a few things that aren't so great:
-inefficient regulation on 1x18650
-complicated UI
-on 2x16340, the XM-L strobes instead of using the low voltage indicator, and cannot switch down to a lower mode
-on 1x18650, low voltage indicator comes on a little too late

Now for some explanation of these.

I've seen too many lights with large heads that are obviously designed to be throwers, but for some reason the manufacturer gave it a textured reflector instead of SMO. I don't know why anyone would do that, if you want to throw, make it throw. At long distances, nobody's going to be bothered by imperfections in the beam. Sunwayman's done the right thing with the reflector here, thrower all the way. And even at close distances, there are a few rings and beam artifacts you can see on a white wall, but even then it's not so bad as to be distracting. The emitter is well centered and the reflector is well shaped. Also, the tint on these is great. All other U2 binned lights I've seen have been severely tinted. This is a cool white for sure, and you can see a little pinkishness to the beam on a white wall, but for the most part the beam is just cool white, and I like that.

The candle mode is nice, it gives a great even flood over the room for indoors use. With the head on, it's pretty hard to use the light at close range because the spot is so bright compared to the spill. While the T20CS wouldn't be my first choice to use indoors, it's nice to have the option to take the head off and use it for flood if it's the only light I have with me. Having the emitter recessed a bit helps keep the beam from getting in your eyes at that point, too.

The performance on 2x16340's isn't too shabby, considering Sunwayman doesn't officially list them as a power source for this light. They are very well regulated, and the brightness hardly drops at all before the cells are depleted. I don't like that it strobes and gets stuck on the current mode when the batteries get low. If Sunwayman wants to officially support these in this light or a similar one in the future, they'll have to find a way to activate the low voltage indicator at a limited voltage range up there, in addition to the low voltages for 1x18650.

The performance on 1x18650 is better than I expected, but I'd still like to see the regulation be a bit better. With the low voltage indicator, there's no reason for the light to dim before it turns off, that's just a waste of energy. On lights without a low voltage indicator, the dimming helps let you know it's time to replace the battery before the light just shuts off. With the T20CS, I'd rather have flat regulation to get maximum brightness as long as possible, and let the low voltage indicator tell me when the battery is low. That same idea goes for using 2xCR123.

On the topic of the LVI, we've had a bit of a discussion in the posts below, which you can read for more details if you like, but I'll just give my summary here. The voltage that turns on the LVI varies between modes from about 3.4V to 3V. Lithium-ion cells have a useful capacity range from 4.2V to about 2.5V or 2.8V, depending on the brand of the cell, and that's usually about when a protected cell will turn itself off. In general it's better not to rely on a protection circuit, especially at low currents, because they don't always work perfectly, and it's not good to discharge your lion past that point. Also, it's recommended to not store you lion at voltages below at 3.8V. So, my conclusion on the LVI: it's useful for letting you know when you really need to stop using your cells, and they *should* not be damaged by being depleted to the point where the LVI on the T20CS comes on or starts flashing. However, when it starts flashing, you should probably stop using the cell and charge it up right away, especially if you're not using a protected cell. Ideally, the LVI could come on solid at a higher voltage (around 3.7V maybe) to let you know that you'll need to charge your battery before you store it, then start flashing around 2.9V or 3V. So, while not ideal, it does the job of letting you know when you need to switch to a different battery just fine.

The UI on the T20CS is very different from what's making Sunwayman popular, their simple and intuitive control ring lights. This UI is definitely not simple, but it manages to accomplish a lot of function in a package that works well together. You can always get to max output quickly, but lower modes are still available for extended run time. It's got strobe and SOS available, but they don't get in your way if you don't want them. Few things are more annoying than having to cycle through a strobe mode in order to get to low, and with the T20CS that won't be a problem. Before reading the manual I played with the UI a bit just to form an impression on my own, and once I accidentally activated the strobe when I didn't want to. That's not fun, but I just turned it off, and when I turned it back on it was no longer strobing, so I was happy. This UI takes a little time to learn, but not much. I can't hand it to a friend and have it just work for them, but I can explain it to them and they can master it within 5 minutes. I'll put more details in the "Tactical" section of the review, but for now just know that while it isn't a "simple" UI, it works well and is fairly intuitive once you learn it.

I appreciate the effort that went into designing this light, and the attention to detail is great. This is the sort of light that I can count on working well every time, and look good doing it.

Tactical

"Tactical" is a word that get's thrown around a lot, and everyone has their own idea on what a "tactical" light should be. Before writing this I did a fair amount of research on old threads looking into what the CPF community in general thinks a tactical light ought to be, so this is a combo of that and my own opinion.

When it comes down to it, a tactical light is one that can be used to execute tactics. You have a plan, and the successful execution of your plan depends at least in part on your flashlight working as you plan for it to. What you look for in a light to use for your tactics depends largely on what you're trying to do, and the environment you'll be in. For example, sneaking up on enemies will require a flashlight that has a low low available easily, searching a crash site for survivors requires a light that has a high output available easily. Indoors or close up you generally want a floody light, outdoors or for long distances you generally want a hotspot that can throw far, etc. So, the appropriate light for your tactics will largely depend on what you're trying to do. However, a few things remain constant for all lights in the "tactical" class...

1. Reliability. In order to be able to rely on your light to be a part of your tactics, you need to know that it will do what you expect it to. Flickering, entering the wrong mode, not turning on, accidentally turning on, etc., is not acceptable. The light needs to work just like you expect. Many people desire simplicity in a tactical light, which is understandable, but not necessary for all situations. A complex UI can be very useful if you know it well. Complex devices are useful in tactical situations all the time, it's up to you to decide whether or not your situation needs a complex flashlight or a simple one.

In this area, the T20CS does very well, because it can operate either as a simple device or a complex one. For a simple UI, just use the tail cap switch, and never touch the side switch. Max brightness all the time, silent momentary on or click into constant on. Simple.

If your situation needs a more complex device, the T20CS can do that with the side switch. Turn the T20CS on with the tail cap switch, then off with the side, and you are in standby mode, ready to enter into any mode you like. A key feature here is that you don't have to mess with strobe modes when you don't want them, but if you use strobe frequently, it's quick to get to with a double click on the side switch. One downside here is that when using the side switch, you can't get to max output as quickly as I like. In order to get to turbo mode when you've been in one of the other modes, you have to click the tail cap switch off then back on again. I'm not sure how that could have been designed differently, but it's something to keep in mind. In general, though the UI with the side switch is complex, you can learn it easily, and it will perform as you expect it to when it counts. Consider it part of your training for your tactical situation.

2. Durability. A tactical light needs to be able to stand up to whatever stress the environment is going to put on it. Again, this varies depending on what you're doing (a dive light needs different qualities than a light being used around EM pulses), but in general you know you want it to be impact resistant, sturdy, water resistant, etc.

The T20CS does very well here. Not to much to say, other than it's a solid light, and I feel confident it won't break easily. You can keep an eye on the "Long Term Impressions" section for any updates in this area.

3. Adaptability. While a tactical situation means you are executing a pre-formed plan, we all know that things don't always go according to plan. Equipment you use in a tactical situation needs to not only be enough for your plan, but enough for any possible/likely bumps in the road.

The T20CS is fairly adaptable, probably more so than many lights called "tactical". As I mentioned earlier, the UI can either be just a single mode with momentary or constant on, or if needed you can start using the other modes as well. If your situation changes, you have one light with the ability to fill many roles. Also mentioned earlier is the candle mode, for a floodier style light. While not the ideal solution for switching from throw to flood, it works in a pinch. Finally, the many battery combos available make it adaptable as well. I plan to use 1x18650 for most work with it, and have 2xCR123 available in case I don't have time to recharge my lions.

In the end, only you can decide whether this light is appropriate for you tactics. My opinion is, it's definitely a good one to have as an option

Note: As of Dec. 2011, Sunwayman has announced two remote pressure switches that would be compatible with the T20CS, but are not yet available for purchase, the AP01 and AP02.
Thrower

As you can tell from the beam shots, the T20CS is a great thrower, with very respectable spill on the side. I found that I could see objects very far away lit up very well, and was still able to illuminate the area around me. The T20CS isn't pure throw, the reflector could be tweaked a bit more or the head made slightly larger in order to send more light down the hotspot. However, for such a compact size, it throws great. Personally, I wouldn't want to make it much more throwy, I like that I can still see what's going on near me.

I was most impressed when the T20CS was able to light up the silo that was about 1/3 mile down the road. It wasn't extremely well lit, but I could see that it was there, and I could see it well enough to detect whether or not there was movement on the face of it. In normal use, I found that I could see well what was going on at about 225 yards, and identify objects at about 275 yards.

So, while not a purely throw dedicated light, you'll be hard pressed to find a better thrower in such a small size, and the amount of spill it has makes it useful for more tasks as well.

Long Term Impressions

I'll fill this part in after carrying the light for a while. If nothing get's added here, either I find nothing else worth noting about the light, or I end up not using it often.

2/8/12
-I appreciate the instant turbo from the tail cap more and more every day. I recently took some beam shots in a sketchy part of town, and liked knowing that I had turbo quickly available without having to fumble for it.
-The grip ring gets caught in the holster a bit some times, which I don't like because it makes it hard to pull the light out quickly. Not a huge issue, but I do wish it came out easier. I wouldn't want to remove the grip ring, because I really like the good grip.
-Here are some bonus beam shots for fun:

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Many thanks for this GREAT review! I'll be checking back to see the rest of it since I have my eye on this light. The size, shape, output, ui, battery life all seem good. I'm ok with running cr 123's if that gets the right output, but it seems as though actual runtime might be less than what they advertised. This is great to see thanks again!

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Hi Mac, it would have been nice if SWM had made it where a seperate LED on the side of the body blinked slowly when it reached 3.80, then faster at 3.70 etc. Or how's this for a concept: have a little digital LED that gives you the exact voltage at all times! press a button for a dim blue backlight. Hmmm... who wants to start a flashlight company with me? Sorry for my arrogance, it just seems that I'd like to 'know' a little beforehand, who's with me on this one? The only time they got it right was with the M40C at around 3.67 V, the light comes on. They have the technology. I mean why not use it on ALL the lights?

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Originally Posted by Lou Maan

Hi Mac, it would have been nice if SWM had made it where a seperate LED on the side of the body blinked slowly when it reached 3.80, then faster at 3.70 etc...

This is actually what it does, except not at those voltages. There is a small red LED on the side of the body that turns on when the battery gets low. I'll edit my description of it to make that more clear.

Your other ideas sound good too, though no doubt more expensive to implement

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

great review bigmac 79! I look forward to the beamshots! thanks for taking the time so that all of us that dont have it yet can subjectively make a decision to buy ...or not to buy.. that is the question lol

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Very nice review BigMac! Looking forward to the beamshots also!! Looks like this type of light-class is going to be next in line... Apparently the market's calling for longer throwing brighter tactical lights... Just saw a posting for the Klarus XT11... looks like another potential contender in this class of light - depending on throw. That's the part I'm most anxious to hear about from your review. Hoping to hear 220 yards with good visibility.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Thanks for the clarification on the low voltage indicator Bigmac! Yeah, that's I guess what I do with my M40C, if I'm using low or medium for an extended period and I'm getting concerned, I just flip it to high for a few seconds to see if the indicator lights up and if it doesn't, then I'm good for a little while longer. This way, you get the earliest possible warning so you don't discharge so deeply. I usually like to recharge anywhere between 3.6 and 4.0 preferably nearer the latter. Is this good practice? I guess not much difference between 3.6 and 3.3 as after 3.6 it's empty and drops quickly. Just want my batteries to last and not to make them too angry/unstable.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

You're right that you can use the higher modes to get an earlier low battery warning, I've found myself doing that with the T20CS.

I'm not a battery expert, but from my understanding, discharging your li-ion to the point where the protection kicks in won't hurt it, and you're more likely to decrease the lifetime of your cell by over-charging it. I've heard a lot of people say they like to only charge their li-ions to 4.15 or 4.16 V (if they have a charger they can do that with) as it makes them last longer. I imagine if you're only using the cell from 4.15 or 4.2 V down to 4.0 V you're not getting a lot of runtime, and maybe decreasing the lifetime of your cell by charging it more often than necessary.

Again, though, I don't know a ton about batteries, so someone else might be able to answer your question better. I'll just say that you should be fine waiting until the indicator comes on before you change cells.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Alright, I've added a ton of pictures and information, and a couple of videos. The only thing left is to do the beam shots, then I'll move on to the subjective review. It looks like we'll finally get a clear night tonight, so this might be my chance.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

great review ! reminds me of a surefire Z2 on steriods, nice ! do you only have trustfire 18650, i need some not sure what to buy, are you happy with there performance in a high output light like this ?

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Great reviews BigMac.
On a V10R or V20C XM-L's, the amperage is low; around 1.5 amps or even less.
On this T20CS with 658 lumens, the amperage is high; or close to 3 amps.
The electronic circuit will add to the amperage too.
Do you notice any flickering, or your Trustfires and XxxFires playing up?
Coz it played up on my SC600 with 750 lumens OTF.
Do you have any reputable AW or Redilast 2900/3100 mAH batteries to test? Because they may give you greater output too.
Callieskustoms are also high quality Panasonic cells, with aftermarket protection circuits added, but at a cheaper price than the others...

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Every battery, not only Li-Ion, has got an internal resistance. Generally good and new batteries have a low IR, and it increases with age (and low temperature). Cheap batteries often have a high IR.

A battery with a high IR can have a good performance when you don't need a lot of power, but if you need a lot of power, it will suck.

Example: Alkaline batteries power your clocks just fine for years and years, but in a high power LED light they will only last a very short time. The energy is right there in them, but it can't be extracted fast enough because their IR is way higher compared to eg eneloops or energizer lithium.
Btw: Zinc-Carbon batteries are even worse than alkalines in this regard (by far, actually). Don't ever ever buy cheap batteries that don't say alkaline on them or the packaging. They are not worth it. They don't have a single advantage and they are much more prone to leakage, too.
Another example with extremely much stored energy but no available power are SAFT batteries.

In a light like this you need batteries with a low IR.

You might wonder why am I writing this? Because IR is the key to understanding what I'm gonna say about the low-battery warning.

When you run your light, a current is drawn from the battery. The battery's voltage sags according to Ohm's law.
Ohm's law says V=R*I, that is Voltage equals Resistance times Current.
So, if you double the current, the voltage sag will double. Voltage sag is proportional to current draw (and internal resistance).

Example: Your battery is a 18650 Li-Ion with an IR of 0.2 Ohm and a voltage of 4.2 V when fully charged.
You draw 1 Ampere from the battery. The voltage sag is 1A * 0.2Ω=0.2V . In this example the battery's voltage under load will be 4.2 V - 0.2 V = 4.0 V.

A battery's voltage under load is basically resting voltage (what you measure when you take it out of the light) minus voltage sag.
Voltage sag is proportional to current draw and IR. IR also varies with the battery's charging state, btw. (If you read this, you probably already guessed it, there are a lot of factors that determine IR of a particular battery. But we don't really need to care about them here. All we need to know: Good batteries will have a lower IR than junk like most of the ****fire stuff.)
So, the more current draw, the lower the voltage under load is.

With this knowledge we're nearly there

[Everything below is specific to Li-Ion]

Now we need to know what a protection circuit does.

It's very simple: It measures the voltage of the battery. The real under-load voltage.
If this voltage reaches a pre-determined threshold (can be different depending on the circuit) the battery is shut off.
The threshold is set to a voltage that is noticably lower than any healty resting voltage for a Li-Ion battery.
But since in actual use there is battery sag, the resting voltage will stay in the healthy area if the current (and thus the difference between voltage under load and resting voltage) is big enough.

Examples (NOTE: not necessarily realistic numbers, I made them up for this example only, but they might be close to reality):
The threshold could be 2.5 V and the Voltage sag 1V (big current). When the protection kicks in, the battery will have a no-load resting voltage of 3.5 V. (And maybe rising a bit if you let it sit some minutes).
With the same battery, at a lower current the Voltage sag could be 0.2 V (small current). When the protection kicks in, the battery will have a resting voltage of 2.7 V.
Now if we compare these examples, in the first case the battery is at 3.5 V. That's completely empty but not damaged.
In the second case, we have the very same battery, in the very same light, but used in a low level until the protection kicked in.
A resting Voltage of 2.7 V is way too low. This battery is completely dead. It needs to be disposed off. The protection didn't protect it.

This is all we need to know to evaluate this statement:

discharging your li-ion to the point where the protection kicks in won't hurt it

Short answer: true on high power settings, very wrong on low power settings.

If you run your light in turbo, voltage sag will be so big that there might even be some useable energy left in the cell when the protection kicks in.
If you run your battery into protection in moonlight mode, there's not only no energy left, but the cell was virtually tortured to death slowly.

And now to what I think about the battery warning feature implemented into the light in question:

Bigmac, if your voltage readings are correct, and I understand your text correctly and my knowledge about batteries (and what I wrote above) is correct, then the low battery warning in this light is implemented completely wrong in order to save LiIon batteries.

In the lower modes the warning only comes on at lower battery voltages. It would need to be the other way around. See my moster text above if you want to know why.
In my opinion the values are way too low in Med and Low.

I would recommend to only rely on this warning function in Turbo and High mode if you want your expensive 18650 to last. Exceptions are the new chemistries that are said to be able to survive discharging to incredibly low voltage levels (compared to other similar Li-Ion).
Don't run your batteries down until the light starts flashing in Med and Low.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Thank you, Bigmac_79, for the video on the interface. It clears up my confusion. Though, the interface looks busy, but I haven't tried it out myself yet so I can't make any judgement.

You're welcome

I'll elaborate on my opinion as I finish the review, but basically, while I think the UI isn't as simple as I would like, it works well as a tactical interface.

Originally Posted by zs&tas

great review ! reminds me of a surefire Z2 on steriods, nice ! do you only have trustfire 18650, i need some not sure what to buy, are you happy with there performance in a high output light like this ?

The only 18650 cells I have right now are the Trustfire Flames 2400 mAh from DX. For the price I paid for them, I am very happy I would love to have some higher quality cells that could perform better in high output lights like this, but that's just not in the budget right now. If you can afford it, I would recommend something better quality, but if not, these will get the job done.

Originally Posted by peterharvey73

Great reviews BigMac.
On a V10R or V20C XM-L's, the amperage is low; around 1.5 amps or even less.
On this T20CS with 658 lumens, the amperage is high; or close to 3 amps.
The electronic circuit will add to the amperage too.
Do you notice any flickering, or your Trustfires and XxxFires playing up?
Coz it played up on my SC600 with 750 lumens OTF.
Do you have any reputable AW or Redilast 2900/3100 mAH batteries to test? Because they may give you greater output too.
Callieskustoms are also high quality Panasonic cells, with aftermarket protection circuits added, but at a cheaper price than the others...

I've not noticed any flickering with any cells, or any other problems with the performance. I just believe that highe quality batteries will be able to sustain higher outputs for longer periods of time. I've seen a little info on Callieskustoms cells, I need to check out the pricing on those.

Originally Posted by Helmut.G

On the matter of batteries:
...
...
...

Thanks for sharing your knowledge of batteries! As far as I know, all the facts you've shared are true. On the higher modes, there will be more voltage sag (and I have definitely observed that in my tests, the voltage measured across the battery rises quickly after I turn off the light), and on the lower modes, there will be less. However, I'm not prepared to agree with your final assertion until I've looked into the specifics a little more. Your example makes sense, but the actual numbers are what's important, so we can't afford to guess. I'll do some research. What I need to find out is: the voltage it is "safe" to discharge a li-ion cell to, the voltage that is "healthy" for the cell to discharge to, and just how much the current sags on the lower modes.

Here's why. The voltage sag acts as a buffer for the protection circuit. The low voltage indicator on the T20CS sees the same sagged voltage as the protection circuit sees, so the "real" (resting) voltage of the cell will always be at least slightly higher than the voltage under load, and slightly higher than what the protection circuit and low voltage indicator see. This means that as long as the protection circuit is set to cutoff at a high enough voltage (greater than the healthy discharge voltage for the cell) then there won't be any problems.

For example, if it is safe to discharge a cell to 2.75 volts, and the protection kicks in at 2.8 under load, the resting voltage will actually be higher than 2.8, which is also higher than 2.75.

And anyway, if it isn't safe to run a cell down to the voltage where the protection kicks in, even under very small loads with little voltage sag, then that seems to me to be a problem with the voltage the protection circuit is set to, not the low voltage indicator on the T20CS.

I'll look into it more, but according to this page: http://www.candlepowerforums.com/vb/...ead.php?308451, it looks like for many brands of cells, there is still a small amount of usable capacity below 3V, which is about where I measure the T20CS's low voltage indicator to come on when in low mode.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

I sense you will be getting many free lights in the future if you keep up these excellent reviews. Bigmac, that is either one very small light or you really live up to your name with massive hands. Usually we'll call someone who is big: "Tiny Tim" or something. I don't know. What do I care. Just an observation.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

[...] but the actual numbers are what's important, so we can't afford to guess. [...]

Agreed.

Here's a small quote from AW's battery sales thread, there are numbers on how much energy is available at certain voltages and advice on how to treat LiIon batteries:

Originally Posted by AW, in battery sales thread

[...] Please keep the voltage of all LiIon batteries above 3.8V for healthy storage. Recharge as soon as possible when you have run them down. Storing a depleted ( less than 3.6V open voltage ) battery may damage/ shorten life/cycle permanently.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

BigMac, I noticed you added some nice photos.
With a 38mm bezel diameter, the T20CS is still a tad relatively small-medium in size rather than a true medium size like an RRT-1 or RRT-15 with a 48mm bezel diameter, however all that is relative only.

Helmut was saying something similar about how the cheaper low quality batteries have more internal resistance, thus a slower discharge rate, hence a lower amperage, which generally means less lumens too.
Notice how the Ultrafire 16340's are only drawing 0.998 amps on turbo?

In general, the bigger 18650 will have lower internal resistance, and a faster discharge rate, with a higher amperage, than a 16340.
Thus 1.96 amps on the 18650 versus just 0.998 amps on the 2x16340 Ultrafires.

Rechargeables tend to have a lower internal resistance and faster discharge rate with higher amperage than disposable batteries.
Here, at 0.998 amps, the Ultrafire 16340's may be underperforming relative to the Energizer 2xCR123's?
However, we can try an AW 16340 750 mAH Protected from AW himself:http://www.cpfmarketplace.com/mp/sho...read-*Part-12*
He is very reliable; I live in Australia, and I normally receive them in 8 working days, in a nice plastic 2x18650/4x16340 container too!
The AW's are used as a benchmark by Selfbuilt etc.

BM, with the lower current draws on turbo mode, do you notice less lumen output too?
Because when I used Ultrafire 18650 2400 mAH Protected on my SC600, it was less bright than when I used quality Redilast 3100 mAH Button Tops.
The quality Panasonic cells with aftermarket Jap IC Protection circuits have lower internal resistance, and so deliver a higher amperage to my hungry SC600 with 750 lumens OTF, than my Ultrafire 18650's...

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Bigmac,

Thanks for the clear review. Sunwayman seems to be on target with this one.
1 point I dislike, there is no way to set the strobe in memory.
From my point of view, that is a reason we can't use this light for our work.
I look forward to the subjective Review thou, specialy the Tactical part.

Re: Object/Subject Review: Sunwayman T20CS (In Progress)

Originally Posted by Bigmac_79

The only 18650 cells I have right now are the Trustfire Flames 2400 mAh from DX. For the price I paid for them, I am very happy I would love to have some higher quality cells that could perform better in high output lights like this, but that's just not in the budget right now. If you can afford it, I would recommend something better quality, but if not, these will get the job done.

.

ok thanks, just got my first 18650 light got some cheaper ultrafire 3100 for now just so i have avaliable juice, ill prolly get an aw2900 in a few months.